An organic thin film for an organic EL display device or a low-molecular type organic EL light emitting device such as an organic semiconductor laser is usually formed by vacuum vapor deposition.
As shown in FIG. 7, a vacuum vapor deposition apparatus for use with vacuum vapor deposition includes a vacuum chamber 51, a vapor source 52 provided at a bottom portion in the vacuum chamber 51, and a substrate holder 53 disposed in an opposing relationship above the vapor source 52.
In order to form an organic thin film on the surface of a substrate S using such an apparatus as just described, the substrate S is mounted on the substrate holder 53 with the surface thereof directed downward. Then, while the surface of the substrate S is covered with a mask (not shown), organic raw material is heated to evaporate from the vapor source 52 in the vacuum chamber 51 in high vacuum of 10−3 to 10−4 Pa. Consequently, the organic raw material is vapor-deposited on the surface of the substrate S as indicated by arrow marks D in a state wherein the source gas is diffused sufficiently within the vacuum chamber 51.
Meanwhile, in recent years, as an apparatus for forming an organic thin film, an organic vapor phase deposition apparatus based on organic vapor phase deposition (OVPD) has been proposed (PCT International Publication for patent application Ser. No. 2001-523768).
The organic vapor phase deposition apparatus includes a vacuum chamber, a substrate holder provided in the vacuum chamber, and a gas supplying apparatus disposed for supplying gas into the vacuum chamber. Source gas is supplied together with carrier gas to the surface of a substrate-mounted on the substrate holder within the vacuum chamber under a decompressed atmosphere to form an organic thin film on the surface of the substrate.
Where such a vacuum vapor deposition apparatus and an organic vapor phase deposition apparatus as described above are used to form an organic thin film, if an organic thin film is formed while the substrate is in a stationary state, then the source gas cannot be deposited uniformly on the surface of the substrate, but the film thickness of the organic thin film formed becomes ununiform. Therefore, a rotating mechanism or a sliding mechanism is provided for the substrate holder to adjust the film thickness distribution.
However, since, in the vacuum vapor deposition apparatus, source gas evaporated from a vapor source within the vacuum chamber is supplied in a diffused state toward the substrate disposed above the vapor source, even if a rotating mechanism or a sliding mechanism is provided for the substrate, there is a tendency that the source gas is likely to be supplied to a central portion rather than end portions of the substrate.
Meanwhile, in the organic vapor phase deposition apparatus, since source gas is supplied in a vapor phase state into the vacuum chamber, the source gas supplied through a gas supply port is likely to flow along the shortest path toward an exhaust port. Therefore, in order to supply the material gas uniformly to the surface of the substrate, it is necessary to move the substrate mounting face with respect to the gas supply port taking the flowing direction of the source gas into consideration.
Accordingly, a thin film formation apparatus is demanded by which source gas is supplied uniformly to the surface of a substrate so that an organic thin film of a uniform film thickness can be formed on the surface of the substrate.